Solenoid Valve Assembly for a Combustible Gas Supply Device to an Endothermic Engine

ABSTRACT

The solenoid valve assembly ( 5 ) presents an inlet union ( 8 ), at least one combustible gas outlet hole ( 28 ), and a plate ( 29 ) carrying a shutter ( 13 ) and operatable by an electromagnet ( 19 ) for controlling the solenoid valve ( 14 ). The plate ( 29 ) is turnable about a contact line ( 36 ) of one face ( 37 ) engaged by a bar ( 46 ) pushed against the plate ( 29 ) by a helical compression spring ( 44 ), so as to normally keep the shutter ( 13 ) in closed position. A valve body ( 7 ) is connected to an intermediate plate ( 12 ) carrying the outlet holes ( 28 ) and is closed by a removable and modular closing plate ( 9 ), which carries a variable number of outlet conduits ( 1 ). The intermediate plate ( 12 ) is provided with a series of grooves ( 56 ) adapted to accommodate a series of different gaskets ( 17 ), each corresponding to a module of the closing plate ( 9 ).

TECHNICAL FIELD

The present invention relates to a solenoid valve assembly for a combustible gas supply device to an endothermic engine, comprising at least one solenoid valve adapted to be controlled to send the combustible gas to a corresponding engine cylinder.

BACKGROUND ART

There have been proposed different combustible gas supply systems to an engine. In a known system, the gas output by a reducer-vaporiser is sent to a distributor-metering unit connected to the intake conduits of the various cylinders, by means of respective conduits. The combustible gas is sent to the intake conduit of each cylinder, by means of a solenoid valve assembly, in which the shutter of each solenoid valve is carried by an anchor of an electromagnet, formed by an oblong plate turnable about a contact line with one edge of a fixed element. Such contact is ensured by a bar of elastic material acting on one end of the anchor, which is however held in closed position by a spring acting at the shutter.

These solenoid valves present some functional limits. Firstly, the position of the contact line on the anchor may vary due to the machining and assembly tolerance of the parts. Furthermore, the presence of the solenoid valve closing spring makes the operation of the latter relatively slow. Finally, the manufacturing of the solenoid valve is relatively costly, and the assembly and maintenance are particularly complicated.

It has also been proposed a solenoid valve assembly for a combustible gas supply device, comprising a solenoid valve having a shutter carried by a plate turnable about a contact line with a fixed element. This contact line consists of an edge formed by a slanted plane portion on a face of the plate, which is held in closed position by a bar of elastic material acting at the slanted plane portion. To extend the limits of the amount of gas to be supplied, for each cylinder of the engine are envisaged two selectively operable different solenoid valves.

This solenoid valve assembly, in the case of an oily fluid such as LPG type gas, presents the drawback that the oil becomes very viscous at low temperatures, for example at −40° C., in consequence of which the gas supply becomes problematic. Furthermore, at low temperatures, also the elastic features of the returning bar are reduced, whereby the anchor is returned to closed position with great delay. The elastic bar provides in all cases a non constant force at various temperatures of use, for the detachment from the polar surface of the electromagnet core. Finally, the presence of two solenoid valves for each engine cylinder makes the device cumbersome and costly.

DISCLOSURE OF INVENTION

It is the object of the invention to obtain a solenoid valve assembly for a combustible gas supply device, resulting in high reliability and low cost, eliminating the drawbacks of the solenoid valve assemblies of the known art.

According to the invention, this object is achieved by a solenoid valve assembly for a combustible gas supply device to an endothermic engine, as defined by claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, it will now be described a preferred embodiment only by way of non-limitative example, and with reference to the accompanying drawings, in which:

FIG. 1 is a prospective view of two solenoid valve assemblies according to two variants of the invention;

FIG. 2 is a longitudinal section of a further variant of the solenoid valve assembly according to the invention;

FIG. 3 is a partial section taken along line III-III in FIG. 2;

FIG. 4 is a portion of the section in FIG. 3 on a magnified scale;

FIG. 5 is a section taken along line V-V in FIG. 2;

FIGS. 6 and 7 are a view of two details of the solenoid valve assembly in FIG. 2;

FIG. 8 is a section taken along line VIII-VIII of the solenoid valve assembly in FIG. 2;

FIG. 9 is a partial longitudinal section of one of the variants of the solenoid valve assembly in FIG. 1;

FIG. 10 is a partial longitudinal section of the other variant of the solenoid valve assembly in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIG. 1, numeral 5 generically indicates a solenoid valve assembly according to two different variants of the invention, for a combustible gas supply device to an endothermic engine, for example an Otto cycle. The combustible gas may be methane or LPG. The assembly 5 is enclosed in a box 6 essentially shaped as a parallelepiped, which comprises a hollow body 7 (also see FIG. 2), on which an inlet union 8 is fastened in a known manner for a rigid or flexible gas inlet conduit, not shown in the drawings.

The box 6 also comprises a plate 9 for closing the hollow body 7, which supports every time a number of nozzles, or outlet unions 10, for as many rigid or flexible outlet conduits, also not shown. Each of these outlet conduits is connected in a known manner to a corresponding engine cylinder. In FIG. 1, in one of the variants, the plate 9 carries only one outlet union 10, while in the other variant the plate 8 carries four outlet unions 10. In FIG. 2, the plate 9 carries instead two outlet unions 10. In any case, the outlet unions 10 are calibrated and interchangeable, and are gas-tightly removably fastened, for example screwed, onto corresponding threaded pipes 11 made on the plate 9.

The box 6 also comprises a spacer or intermediate plate 12 supporting a plurality of shutters 13 for as many solenoid valves 14. Each solenoid valve 14 is associated to corresponding holes 28 of plate 12. The holes 28 are reciprocally equal and parallel and present respective axes arranged on a longitudinal median plane P (also see FIG. 3) perpendicular to plate 12. This plate is fastened to the hollow body 7 by means of screws 15, with interposition of a gasket 16. In turn, the closing plate 9 is fastened to the intermediate plate 12 with interposition of gaskets 17, which will be better seen below, by means of other through screws 18, which are fastened in corresponding threaded holes of the hollow body 7.

In particular, each solenoid valve 14 comprises a control electromagnet 19 (FIGS. 3 and 4) comprising a core 20 of magnetic material, and an electrical coil 21. The core 20 presents a polar surface 22, and is fastened onto a bottom wall 23 of profile 24 (also see FIG. 7) also of magnetic material, which completes the magnetic circuit of the electromagnets 19. The profile 24 is common to all cores 18 and is accommodated in a compartment 36 of the hollow body 7, in communication with the inlet union 8. The profile 24 also presents a side wall 25 having a polar surface 26, flat and aligned with the polar surface 22 of the core 20. A gap plate 55 (also see FIG. 6) comprises a strip 45 adapted to cover the surface 26 of the wall 25 and a series of appendixes 40 adapted to cover the polar surfaces 22 of the cores 20.

Each shutter 13 is in the form of an elastomeric material disc and is adapted to close the corresponding hole 28 of the intermediate plate 12. Each shutter 13 is carried in a known manner by a corresponding anchor 27 of the respective electromagnet 19, which is formed by a plate 29 of magnetic material. The plate 29 has an oblong shape and presents a face 31 consisting of a flat surface, from which the shutter 13 protrudes towards the hole 28. The plate 29 is provided with a pair of lateral recesses 32 (FIG. 5), which are adapted to engage two appendixes 33 carried by a rib 34 of the intermediate plate 12, whereby this plate 12 has the function of guiding the anchors 27. To the wall 25 (FIG. 3) of the profile 24 is anchored the usual printed control circuit 35 of the solenoid valves 14, which is therefore accommodated in the compartment 36 of the hollow body 7.

The plate 29 is turnable about a contact line 36 arranged on a face 37 of the plate 29, opposite to face 31. The contact line 36, through the strip 45 of gap 55, rests on the surface 26 of the side wall 25 of the profile 24. The face 37 comprises a flat surface 38 parallel to that of the face 31, a slanted surface 39, and a strip 41 formed by a curved surface. The strip 41 comprises the contact line 36 and is arranged between the two flat surfaces 38 and 39. Preferably, the dihedral angle between the two surfaces 38 and 39 is smaller than 20°. On a portion 42 of the face 31, opposite to the slanted surface 39 of the face 37, acts an elastic element, generally indicated by 43, which is adapted to normally keep the shutter 13 in closed position of the hole 28 of the intermediate plate 12.

According to the invention, the elastic element 43 comprises a helical compression spring 44, which by means of a rigid compensation plate 50, acts on a bar 46 of relatively elastic material common to all anchors 27. In particular, to accommodate each spring 44, the intermediate plate 12 is provided with a corresponding sleeve 47 (also see FIG. 4), engaging a corresponding compartment 48 of the closing plate 9, against whose bottom the spring 44 abuts. At each sleeve 47, the intermediate plate 23 presents a circular groove 51, in which is accommodated a corresponding gas tight gasket 52. Furthermore, the printed circuit 35 is connected by means of a wiring formed by electrical wires 49 having a single connection with the outside. In particular, the wires 49 supply electrical power to the electromagnets 19 and are enclosed in a single sheath 59 inserted in an aperture 60 of the hollow body 7.

Advantageously, the bar 46 presents a section having a circular portion engaging the portion 42 and a flat portion engaging the compensation plate 50. The bar 46 consists of a fluoridated elastomer, having a permanently non alterable reticular structure in a temperature range from −40° C. to +180° C. Therefore, the bar 46 ensures in such temperature range a friction reduction between an elastic element 43 and the plate 29, thus extending the life of the solenoid valve 14.

Preferably, the gap 55 presents a reduced thickness, for example from 0.015 mm to 0.15 mm. For the purpose of increasing drainage of oily fluids contained in LPG combustible gas, each fin 40 of the gap 55 (also see FIG. 6) is provided with a hole 53. For the same reason, each plate 29 is provided with a hole 54. In turn, the coil 21 is sized so as to absorb, during the maintenance step, a power from 1.3 to 1.5 watts. Advantageously, the coil 21 may be sized so as to absorb a maintenance current of 0.6 amperes and an equivalent power of 1.44 watts.

From performed experiments it results that the solenoid valve 14 according to the invention presents an opening and closing time of the shutter 13 lower than 0.6 ms, with a fluctuation of such times lower than the measurable threshold. The maximum injection frequency is higher than 160 hertz, with an average life of the solenoid valve 14 in the order of 500 million operating cycles. In normal conditions of use, the repeatability of the operation of assembly 5 of solenoid valves 14 results constant in a range of temperatures from −40° to +120°.

According to another aspect of the invention, the closing plate 9 is fitted in easily removable manner and is of the modular type, i.e. provided with a different number of conduits 11. For this purpose, the intermediate plate 12 is provided with a set of grooves, indicated as a whole by 56 and adapted to accommodate corresponding gas-tight gaskets 17, for allowing the connection to different closing plates 9.

In FIG. 2 it is shown a plate 9 provided with two conduits 11, each of which ends with an intermediate chamber formed by a flared portion 57 of the conduit 11, so as to be in communication with two holes 28 of the intermediate plate 12. In this manner, each output union 10 can receive the supplied combustible gas, through one or two holes 28 of the closing plate 9, operating one or both the respective solenoid valves 14. The connection of the closing plate 9 on the intermediate plate 12 is made using two gaskets 17, each of which is arranged in a groove 56/2 (FIG. 8), which surrounds the outlet of two holes 28 of the intermediate plate 12.

In the variant of FIG. 9 which shows a section of one of the variants in FIG. 1, it is shown a closing plate 9 provided with a single conduit 11 for a corresponding outlet union 10. The single conduit 11 is in communication with an intermediate chamber 58, adapted to receive the combustible gas. This is supplied, through a number of holes 28 variable from one to four, operating the corresponding solenoid valves 14. The connection of the closing plate 9 on the intermediate plate 12 is performed with the use of gasket 17, arranged in a groove 56/1 (FIG. 8) which surrounds the outlet of the four holes 28 of the intermediate plate 12.

In the variants of FIG. 2 and FIG. 9, the holes 28 in communication with one same outlet union 10 can be controlled selectively, i.e. individually or in combination, so as to modularly vary the flow rate of combustible gas to be supplied to the respective engine cylinder. Furthermore, the holes 28 in communication with a predetermined outlet union 10 can be variably controlled during the supply step of a cylinder, so as to modulate the combustible gas supply according to a predetermined diagram.

In the variant of FIG. 10 which represents a section of the other variant of FIG. 1, it is shown a closing plate 9, equipped with four conduits 11 for as many outlet unions 10. Therefore, each hole 28 supplies a corresponding outlet union 10 under the control of the respective solenoid valve 14. The connection of the closing plate 9 on the intermediate plate 12 is performed with the use of four gaskets 17, each of which is arranged in a groove 56/4 (FIG. 8) which surrounds the outlet of a corresponding hole 28 of the intermediate plate 12.

As shown in FIG. 10, preferably the conduits 11 are reciprocally coplanar. For the purpose of facilitating access to the outlet unions 10, and therefore the respective connection with the respective connection conduits to the engine cylinders, the conduits 11 have an outwardly diverging shape, whereby the ends of the unions 10 themselves are more distanced.

It is therefore clear that with the variants of FIGS. 2, 9 and 10 of the assembly 5 of solenoid valves 14, it is possible to obtain flow rates of gas towards each engine cylinder from 905 Nl/min (standard litres per minute) at the pressure of 1 bar in the case of FIG. 10, to a maximum of 365 Nl/min in the case of FIG. 9. Furthermore, by replacing the single closing plate 9, the same assembly 5 of solenoid valves 14 may be used in different applications requiring the gas supply through a different number of output unions 10. Furthermore, it is optimised the production, storage and management of solenoid valve assemblies 5, specifically for OEM production.

From the above it is apparent the various other advantages of the assembly 5 of solenoid valves 14 according to the invention with respect to the known art. In particular, the assembly 5 of solenoid valves 14 is of reduced dimensions and weight, whereby allowing more freedom of accommodation in the engine compartment of a motor vehicle. Furthermore, such assembly 5 has a higher reliability, the number of active components being essentially halved, i.e. the number of electromagnets 19 and the respective anchors 27. The response time of the electromagnets 19 is also reduced thanks to the sizing of the gap 55 and of the coil 21. Thanks to the increased compatibility of solenoid valves 14 of the oily fluids associated to LPG gas, the response time is constant at temperatures from −40° C. and +120° C. Finally, thanks to the modular plates 9 it is obtained a high application flexibility for flows up to 365 Nl/min at a pressure of 1 bar.

It is understood that various modifications and improvements may be made to the solenoid valve assembly without departing from the scope of the claims. For example, the holes 28 of the plate 12 may be differently arranged, while in the variant of FIG. 10, the conduits 11 may be reciprocally parallel and coherently arranged with the holes 28 of the plate 12. Furthermore, both the bar 46 and the compensation plate 50 may be divided into individual segments for each anchor 27. The plate 50 may also be provided with narrowing sections to reduce the influence of the shift of an anchor 27 on the adjacent anchors 27.

Finally, both the dimensions and the shape of the box 6 may be changed. For example, in FIG. 9 the closing plate 9 may have a shape such to allow to obtain a tapered intermediate chamber 58 so as to guarantee that the lamellar flow of gas from the conduits 28 is conveyed to the inlet of the single conduit 11 with minimum loss of load. 

1. A solenoid valve assembly for a combustible gas supply device to an endothermic engine, comprising at least one solenoid valve (14) adapted to being controlled to send combustible gas to the engine, said solenoid valve (14) comprising at least one outlet hole (28) of the combustible gas, one anchor (27) carrying a shutter (13) being operatable by an electromagnet (19) for controlling said outlet hole (28), said anchor (27) being formed by an oblong plate (29) turnable about a contact line (35) with a flat surface (26) of a fixed element (25, 55), said contact line (36) being arranged on a first face (37) of said plate (29) between a first flat surface (38) and a slanted surface (39) with respect to said first flat surface (38), an elastic element (43) acting on said plate (29) with a force so as to normally keep said shutter (13) in a closed position of said solenoid valve (14); characterised in that said elastic element (43) comprises a curved section bar (46) pushed against said plate (29) by a helical compression spring (44). 2-16. (canceled) 